1. Field of the Invention
The present invention relates to a solder ball attaching system and method for micro ball grid array packages, and more particularly, to a solder ball attaching system and method, which is capable of performing a solder ball attaching operation inside a single equipment successively.
2. Description of the Related Art
Recently, semiconductor products, which play a pivotal role for development of industry extending into electric, electronic, machine and aerospace industries, have been developed steadily in the technology.
To manufacture such semiconductor products, it must go through a semiconductor chip manufacturing process for manufacturing a semiconductor chip, a semiconductor chip packaging process for protecting the friable semiconductor chip and signal input output between the semiconductor chip and an external equipment and a testing process.
Actually, the development of the semiconductor chip manufacturing technology and the improvement of performance of equipments of precision process for manufacturing the semiconductor chip have made the manufacture of a highly integrated semiconductor chip possible. Moreover, in the semiconductor chip package process, the development of the semiconductor packaging method and the improvement of efficiency of process equipment for manufacturing the semiconductor package have made the increase of efficiency of semiconductor products and the miniaturization of the semiconductor products.
Especially, a ball grid array package, which is mainly used for the highly integrated semiconductor products having lots of input/output terminals, has been disclosed. The ball grid array package is easier in treatment than a PGA(Pin Grid Array), in which signal input/output between the external device and the semiconductor chip is performed by I/O pins arranged in matrix type. Moreover, the ball grid array package, which is small in size, is what is called xe2x80x9cchip scale packagexe2x80x9d that the whole size of the semiconductor product is about 120% of that of the semiconductor chip, and uses solder balls as input/output terminals in place of pins.
The ball grid array package, in state that the semiconductor chip is attached on a printed circuit board forming circuit pattern on both sides or on a non-circuit side of a flexible board having the other side forming the circuit pattern, connects a bonding pad of the circuit pattern and the semiconductor chip in various way, for example, a beam lead bonding, a wire bonding or others.
At this time, the circuit pattern is connected to a portion of a circuit pattern called as xe2x80x9csolder ball padxe2x80x9d and performs electric signal input/output with the external device through the solder ball pad.
The semiconductor chip is wrapped with molding resin to protect it from external shock and force and a solder ball is attached on the solder ball pad by a solder ball attaching process for connection with the external device.
At this time, the solder ball attaching process is divided into a solder ball seating step that the solder ball is coated with a water-soluble flux and the solder ball is temporarily seated on the flux, a reflow step that the solder ball is melted and attached on the solder ball pad in a furnace of high temperature and a cleaning step for removing water-soluble d-solvent.
The solder ball seating step, the reflow step and the cleaning step are performed by a solder ball attaching equipment group. The solder ball attaching group includes a solder ball seating equipment for the solder ball seating step, a reflow equipment, a cleaning equipment and a loader equipment for storing the cleaned ball grid array package. The equipments are arranged in series and independently operated to perform their own step.
However, each of the unit equipments included in the typical solder ball attaching group are located closely with the related equipments, but as there is a long distance between the unit equipments, the area where the solder ball attaching equipment group occupies is very large.
Moreover, the solder ball seating equipment, the reflow equipment, the cleaning equipment and the loader equipment included in the solder ball attaching equipment group perform only their own process but not perform connection between the previous step and the next step. Therefore, the connection between the steps depends on an operator.
Furthermore, as the unit equipments of the solder ball attaching equipment group are arranged long and the operator must perform the connection between the steps, the operator""s line of movement becomes long, thereby fatigue to the operator is accumulated, the period of time required to attach the solder ball on the ball grid array package becomes long, and the steps are not performed consecutively.
Additionally, even though the solder ball seating equipment is out of order and thereby the insertion of the ball grid array package into the reflow equipment and the cleaning equipment is delayed, as there is no connection between the steps, heating of the reflow equipment and cleaning solution feeding of the cleaning equipment are continued, thereby the equipments are easily deteriorated.
Moreover, additional loader equipment is required for storing the ball grid array package finishing the solder ball attachment. After starting the solder ball attaching process, as the operator must directly transfer all unloaded containers to the loader equipment, the automatization of the solder ball attaching process is difficult.
Furthermore, to transfer the ball grid array package from one step to another step, the ball grid array package must be discharged out from the unit equipment and inserted into the next equipment. If the ball grid array package is discharged out from the unit equipment and inserted into the next equipment, there may cause a bad process, for example, the solder ball to be attached drops down from the solder ball pad. Even though such problem is continued, investigation of the factors leading to the bad process is very difficult.
Additionally, as the unit equipments of the solder ball attaching equipment group perform independently their own step, it is difficult to control the whole solder ball attaching equipment group and thereby lots of time is required for the process and the bad process occurs frequently.
Accordingly, an object of the present invention is to minimize the installation area of a solder ball attaching equipment and to reduce an operator""s the line of movement and the operator""s fatigue by integrating equipments required for a solder ball attaching process in one equipment.
Another object of the present invention is to consecutively perform the solder ball attaching process and to achieve the automatization of process by connecting a previous step and the next step through the integrated equipments.
A further object of the present invention is to reduce the frequency number of the occurrences of the badness made during transfer by minimizing the transfer path of ball grid array packages being applied to the solder ball attaching process through the integrated equipments and not to occur the badness in process by separating the ball grid array packages having the badness from the ball grid array packages having good quality.
To achieve the above objects, the present invention provides a system for attaching solder balls, the system comprising: a base body; base frames unloader for unloading base frames from containers mounted on the base body to seat the solder balls on solder ball pads of the base frames; a solder ball seating device mounted on the base body, the solder ball seating device receiving the unloaded base frames from the base frame unloader, fixing in a designated position, coating with flux, seating the solder balls, sorting the base frames according to quality of solder ball seating and storing the base frames of good quality; a reflow device mounted on the base body, the reflow device loading the sorted and stored base frames and melting and cooling the solder balls; a cleaning device mounted on the base body, the cleaning device receiving the loaded base framed from the reflow device, cleaning the flux remaining on the solder ball pads with cleaning solution and drying the cleaning solution covered during cleaning step; and a base frame loader mounted on the base body, the base frame loader sorting the base frames according to attachment quality of solder ball attached on the solder ball pads of the base frames transferred from the cleaning device and storing the base frames of good quality.
To achieve the above objects, the base frame unloader includes: a container guider formed to extend from the upper portion of the base body to the inside empty space of the base body; a container elevator for lifting the containers stored in the inside empty space of the base body from the inside of the base body upward along the container guider; and a pusher discharging the base frames from the containers mounted on the container guider.
To achieve the above objects, the solder ball seating device includes: a composite unit for receiving, fixing and transferring the base frames unloaded from the base framed unloader; a flux coating unit for coating the solder ball pads of the base frames fixed on the composite unit with the flux; a solder ball seating unit for seating the solder balls on the solder ball pads coated with the flux by the flux coating unit; a transfer unit for transferring the flux coating unit and the solder ball seating unit to the solder ball pads fixed on the composite unit; a sorter unit receiving the base frames on which the flux and the solder balls are seated, the sorter unit sorting and storing the base frames according to quality of solder ball seating; and a waiting unit making the base frames of good quality, which are sorted and stored by the sorter unit, wait till the next step is performed.
To achieve the above objects, the reflow unit includes: a base frame feeder for loading the base frames, on which the solder balls are seated by the solder ball seating unit; a step transfer device for transferring the base frames; a chamber wrapping the step transfer device; a heating device mounted at the inner surface of an outlet of the chamber located oppositely to the step transfer device; and a cooling fan mounted at the inner surface of an inlet of the chamber separated from the heating device in a prescribed interval.
To achieve the above objects, the transfer device includes: a transfer screw extending from the outlet of the chamber to the cleaning device; a bushing for supporting both ends of the transfer screw; a motor mounted at one of the ends of the transfer screw to rotate the transfer screw; a transfer block screwed with the transfer screw, the transfer block moving along the transfer screw by the driving of the motor; and a pick-up module connected to the transfer block, the pick-up module transferring the base frame discharged to the outlet of the chamber.
To achieve the above objects, the cleaning device includes: a transfer device receiving the base frames discharged from the reflow device and transferring them; a cleaning chamber wrapping the transfer device; a cleaning solution feeding device mounted inside the cleaning chamber, the cleaning solution feeding device being mounted upper and lower portions of the transfer device; a drier device for drying the base frames cleaned by the cleaning solution feeding device; and an unloader for unloading the dried base frames.
Furthermore, to achieve the above objects, the present invention provides a method for attaching solder balls of a ball grid array package, the method comprising: a solder ball seating step of unloading base frames attaching base tapes on which solder ball pads are provided, coating the solder ball pads with flux, transferring identified solder balls on positions of the corresponding solder ball pads respectively, transferring the base frame after confirming the position of the solder balls on the solder ball pads, and transferring an empty container, from which all base frames are unloaded, in a designated position; a solder ball reflow step of melting and cooling the solder balls seated on the solder ball pads and transferring the base frames after receiving the base frames from the solder ball seating step; a cleaning step of removing the flux covered on the solder ball pads and transferring the base frames after receiving the base frames from the solder ball reflow step; and a base frame storing step of determining quality of the base frames received from the cleaning step, sorting the base frames according to the quality and storing the base frames in the empty container transferred to the designated position.
To achieve the above objects, the base frames, which finished the solder ball seating step, are transferred in the first direction, the empty container is transferred to the designated position along the second direction, the base frames, which finished the solder ball reflow step, are transferred in the third direction, and the base frames, which finished the cleaning step, are transferred in the fourth direction toward the empty container transferred to the designated position.
To achieve the above objects, the first, second, third and fourth directions are directed in such a manner that the transfer course of the base frames is in the form of a loop.
To achieve the above objects, preferably, the second direction is directed oppositely to the first direction.